1. Field of the Invention
This invention relates to a portable heat sealing apparatus for plastic bags and more particularly, relates to an improved more efficient heat sealing apparatus.
2. Background Information
Plastic bags are sealed by heating the perimeter at the opening to the bag. Heat is applied across the opening, under pressure that melts the plastic and xe2x80x9cweldsxe2x80x9d the opening of the plastic bag. There are plastic bag heat sealers that include drawing a vacuuming then sealing the opening by applying heat to melt and weld the opening together. These devices are complicated and expensive, and have jaws that are heated to melt the plastic bag opening after a vacuum has been drawn in the bag.
There is also a plastic bag heater disclosed and described in U.S. patent application Ser. No. 100/319,174 issued Feb. 22, 1966 to Hutchinson et al, one of whom is the inventor of the invention disclosed herein. This patent discloses a portable plastic bag sealer that has a sealing edge with controlled heat to seal the plastic bag my applying pressure against the opening of the plastic bag with the bag positioned on a surface. The device disclosed is simple in construction and use, and can be operated by one hand of an operator. It provides superior seals to comparable portable apparatus that were previously available.
However this device is somewhat thermally inefficient and can have some exposed outer hot surfaces as are typically exposed in the use of hot cloth irons. The heater is in the form of a T-bar that is heated by ceramic heating elements on either end. The heating elements must generate a considerable amount of heat energy to heat the entire T-bar to attain sufficient high temperature on the heating edge to seal the plastic bag. This results in the entire portable bag sealer becoming hot enough to degrade internal components and thus, shorten the sealers operating life. In addition, the inefficient heater requires substantial power to generate sufficient heat to seal a plastic bag.
It is therefore, one object of the present invention to provide an improved plastic bag sealer that provides more efficient heating of the sealing edge.
Yet another object of the present invention is to provide a plastic bag sealer having an improved heater that provides more uniform heat at lower power inputs.
Still another object of the present invention is to provide a plastic bag sealing apparatus, which reduces heat loss by preventing heat transfer to surrounding components and the surrounding atmosphere.
Still another object of the present invention is to provide a plastic bag sealing apparatus that allows small gauge insulation wire to be used that is less expensive and lasts longer when used at the reduced temperatures.
Yet another object of the present invention is to provide an improved plastic bag sealer having an improved heater that prevents transfer of heat to external components (e.g., the cover) thereby providing a safer sealer.
Yet another object of the present invention is to provide an improved plastic bag sealing apparatus with an improved heater that prevents insulating plastic parts from breaking down due to high operating temperatures.
Still another object of the present invention is to provide a plastic bag sealer having a silicon rubberized heater with embedded heater wires that are clamped in place by insulating plates alone or in conjunction with fiberglass insulation.
Still another object of the present invention is to provide a plastic bag sealing apparatus having an improved heater that provides greater heat transfer to the T-bar edge, and less heat transferred to structural components.
Yet another object of the present invention is to provide a plastic bag sealing apparatus having an improved flat silicon sheet heater having embedded heating wires that provide uniform heating over the entire length and width of the T-bar heater.
Yet another object of the present invention is to provide an improved plastic bag sealer having an improved heater utilizing thermally insulating standoffs that assists in reducing transfer of heat to surrounding components and external surfaces.
Still another object of the present invention is to provide a plastic bag sealing apparatus having an improved tubular rod heater. The improved heater will deliver uniform heat energy concentrated in the immediate area of the xe2x80x9cT-barxe2x80x9dsealing edge. The rod heater design reduces the required input heat and further reduces heat energy loss to surrounding components and atmosphere.
Still another object of the present invention is to provide an improved hand-held plastic bag sealer having improved long life elastic foam support springs for resiliently supporting an elongate T-shaped heater.
Yet another object of the present invention is to provide an improved hand-held plastic bag sealer having integrally formed thermally insulating standoffs on a heater clamping plate.
The purpose of the present invention is to provide an improved portable plastic bag sealing apparatus that is more efficient and user friendly than the model disclosed in the above identified patent.
The plastic bag heat sealing apparatus of the present invention is constructed of a T-shaped (i.e., T-bar) heating element providing a sealing edge that is covered with a replaceable channel having a non-stick, heat resistant and durable plastic coating such as polytetraflouroethylene (TEFLON). The TEFLON coating on the channel is effective to prevent the sealing apparatus from sticking to the plastic material. The top of the T-shaped heater is heated by an improved heater comprised of resilient material having an integral heating wire. The resilient heater covers the entire surface on the top of the T-bar heating element, and is clamped in place with an insulator.
A pair of rails on either side of the heating edge of the T-bar are attached by means of springs that allow the heating edge to pass through a slot formed by the rails to heat a plastic bag positioned on a non-stick surface. The heating assembly is enclosed in a housing which has a centrally located handle used to press the heater down when sealing a plastic bag.
A thermostat is provided to vary the temperature of the hot sealing edge applied to the plastic bar. The thermostat allows continuous adjusting the heat intensity according to the thickness of the plastic bags being sealed. Three different settings are provided. The first setting is for plastic bags or films from one to two mils thick. The second setting is for medium bags or films three to four mils thick. A third setting for thicker bags having plastic material that is six to ten mils thick is provided.
The resilient heater is preferably a rectangular shape of soft silicon material having a heating wire encapsulated in the material. The heating wire is incorporated in the material in a winding path along one side, and winds back along the other side. This provides uniform and even heating over the entire heater and high heat transfer to the T-bar heating element. This results in more uniform heating and lower power to achieve temperatures that provide an efficient seal.
The resilient heating element is also clamped in place, on top of the T-bar heater, and cuts stray heat loss by as much as fifty percent (50%) substantially reducing input power. The reduction in heat transfer to the surrounding components prevents cracking and damage to the components due to mechanical shock loads during rough handling.
In an optional but preferred embodiment of the invention the rails from either side of the heating edge of the T-bar heater are attached by advanced long life elastic foam support springs constructed of a urethane foam such as that known as PORON manufactured by Rogers Corporation of Connecticut. The resilient elastic foam supports do not take a compression set and therefore has a very long spring life. Further the stress loads on the hand held portable sealer are relatively light. These foam springs are an improvement over the stainless steel leaf springs, which after many repetitions, can fail. The elastic foam support springs because of the light stress loads will have a nearly infinite life.
The system is also improved with an integrally formed heater clamping plate and standoffs. The integrally formed clamping plate and standoffs are of a heat resistant thermoplastic resin such as xe2x80x9cFORTRONxe2x80x9d manufactured by Hoechst Celanese Corporation. This material is particularly suitable for use in electrical and electronic devices that require high heat resistance. The thermoplastic clamping plate clamps the heater in place on the T-bar heat sealing element.
In an optional embodiment a rod type heater is used that is lower in cost and more directly heats the T-bar sealing edge of the plastic bag sealer. This heater is a cylindrical rod that seats in a channel or groove in the T-bar heater directly above the heat sealing edge. The cylindrical rod heater is specially designed heater or may be a heater known as a CALROD heater from General Electric Corporation or an equivalent. The cylindrical rod heater is clamped by a plate having a complimentary groove or channel to securely hold the heater in place. An insulator is provided between the heater and clamping plate. Preferably a thermally conductive lubricant or grease is provided in the T-bar channel to maximize heat transfer to the heat sealing edge.
In another optional embodiment the rod heater is a specially designed heater inserted in a passageway in the T-bar. The specially designed heater is comprised of a brass rod covered by a fiberglass sleeve having a nichrome wire spirally wound around it and than returning over a second fiberglass sleeve. The assembly is then covered with a third fiberglass sleeve and then inserted lengthwise through a elongate passageway through the T-bar. The passageway is then sealed with a potting compound that allows the transfer of heat to the sealing edge of the T-bar. This arrangement provides a less costly rod heater and a more efficient transfer of heat to the sealing edge.
The above and other novel features of the invention will be more fully understood from the following detailed description and the accompanying drawings, in which: